Color display system



Feb. 18, 1969 N. D. GLYPTIS 3,428,358

COLOR DISPLAY SYSTEM Filed Sept. 7, 1965 Sheet 25 T- LUMINANCE AMPLIFIERPICTURE COLOR SWEEP H l VOLTAGE 3&

INVENTOR 7/6C%Z24 D; 69 0Z Zx 1 22 w ak M 2% A TTOR/VEYS Feb. 18, 1969 1T s 3,428,858

COLOR DISPLAY SYSTEM Fil ed Sept. 7, 1965 Sheet 2 of 2 m ciigg gig;

S IGNA L OSCILLATOR INVENTOR A TTORNEYS United States Patent ClaimsABSTRACT OF THE DISCLOSURE A cathode ray color display having a singlegun with a phosphor responsive to a condition of the electron beam tovary the color of light output. The condition is established by anauxiliary field having a boundary adjacent the deflection zone, betweenthe zone and the phosphor screen, and generally at right angles to thepath of the electron beam throughout a scan pattern.

This application is a continuation-in-part of my application entitledBeam Deflection Device, Ser. No. 697,240, filed Nov. 18, 1957, nowPatent 3,205,391, dated Sept. 7, 1965.

This invention relates to a cathode ray color display system and moreparticularly to a display system with a color control dependent on acondition of the electron beam.

The cathode ray tube color display devices in wide use today incorporatethree electron guns and have a screen made up of dots of red, blue andgreen phosphors together with an apertured plate or shadow mask locatedimmediately adjacent the screen, which has a masking effect that insuresthat a beam from the appropriate gun strikes the correct color dots. Thethree beam tube is diflicult and expensive to manufacture as it requiresvery precise physical alignment of the gun structures, the aperturedplate and phosphor screen. Other color display systems have been tried,including a rotating color wheel, for example, but have not beensatisfactory commercially.

A principal object of this invention is the provision of a single guncolor display tube utilizing a condition of the electron beam to varythe color of the light output of the device.

In accordance with one embodiment of the invention, a phosphor is usedin the screen which is responsive to an energy characteristic of thebeam to emit different colors. More specifically, the color of the lightmay vary with the velocity of the electron beam, or with the frequencythereof.

In accordance with another embodiment of the invention, a single guntube utilizing the shadow mask has a beam source which establishes aslight diffraction of the beam to correspond with the various colordots. This simulates the three separate sources which are presentlyused, but is substantially simpler and more economical to manufacture.

One feature of the invention is the provision in the color displaysystem of a cathode ray tube having a single electron emitting and beamforming gun means and having a screen with multicolor light outputdependent on a condition of the electron beam, means between the gun andthe screen for deflecting the beam to scan the screen, means between thedeflecting means and the screen for establishing a beam modifying fieldwhich is generally uniform with respect to the field of the beamdeflection means, and a source of beam modifying potential responsive tothe color to be displayed, connected with the field establishing meansfor imparting to the beam a condition modulation to vary the color oflight output of the screen, independently of the scanning of the beam.

Another feature is that the color of the light output of the screen is afunction of the velocity of the beam striking the screen and a grid islocated immediately adjacent the deflecting means having a velocitymodifying potential applied between the grid and the screen.

A further feature is that the deflecting means has an apparent center ofdeflection and the grid is concentric with the deflection center, acontrol voltage on the grid effecting a linear velocity modulation ofthe beam without distorting the deflection field. More specifically, thebeam modifying field has a nonlinearity which is less than an elementalarea of the screen throughout the entire surface thereof. I

In accordance with one specific embodiment of the invention, the energyof the beam is modulated by varying the beam velocity and the screen ismade up of multiple layers of phosphor of different colors so thatelectrons having different velocity penetrate to different layers andexcite different colors of the phosphor. In accordance with anotherembodiment of the invention, the screen has a phosphor which gives offdifferent colors in accordance with the frequency of velocity variationsof the beam.

Further features and advantages of the invention will readily beapparent from the following specification and from the drawings, inwhich:

FIGURE 1 is a diagrammatic view of an apparatus embodying the invention;

FIGURE 2 is a block diagram of a color display system embodying theinvention;

FIGURE 3 is a diagrammatic illustration of a display tube embodying theinvention;

FIGURE 4 is an enlarged fragmentary section of a portion of the tube ofFIGURE 3;

FIGURE 5 is a diagrammatic view similar to FIGURE 3, illustrating amodified tube;

FIGURE 6 is a diagrammatic view similar to FIG- URE 3 illustrating theinvention as embodied in a single gun shadow mask tube; and

FIGURE 7 is an enlarged fragmentary view, similar to FIGURE 4,illustrating the tube of FIGURE 6.

In the parent application identified above, various tube constructionsare shown in which an auxiliary beam accelerating field is established.More particularly, in accordance with an important feature of the parentapplication, the amplitude of scan of the tube may be modified by theestablishment of an appropriate accelerating field gradient. Where theaccelerating field gradient is generally at right angles to the path ofthe deflected beam, a linear velocity modulation of the beam is effectedwhich is utilized to effect a color change of the resulting display.Linear modulation means that the variation in the modifying fieldchanges only the velocity of the beam and does not have a significanteffect on the deflection. By a significant effect on deflection, it ismeant a deflection which would be apparent to an observer and woulddegrade the quality of the picture. If the size of the spot produced bythe electron beam is considered to define an elemental area of thepicture displayed, an irregularity which causes a deviation of the beamless than a beam diameter is generally not significant while adeflection of greater amplitude is.

Turning now to FIGURE 1 of the drawings, cathode ray tube 10 has a gunstructure 11 which forms an electron beam 12. Beam deflection coils 13are located about the neck of the tube 10 and are connected with asuitable source of deflection signals, not shown. The beam is deflectedabout an apparent deflection center 14 to scan the face or screen 15 ofthe tube. A phosphor coating on the inside of the tube face is excitedby the electron beam and gives off light. The deflection signalsconnected with coils 13 may, for example, cause the beam to scan theface of the tube with horizontal lines moving from top to bottom of thescreen, in a manner used with commercial televisiion.

In the tube of FIGURE 1, the beam is deflected at a low energy level asthe grid 16 is operated at a potential much lower than the potential onthe screen of the tube. A second grid 18 is interposed between the grid16 and the screen of the tube. The grids 16 and 18 are parallel and aregenerally spherical in configuration about the center of the deflectionof coils 13. Connected between grids 16 and 18 is a signal source 20which establishes a control potential for the beam velocity. If thesignal from source 20 is rapidly varying, the electrons are bunched asthey pass between the grids at a frequency related to the frequency ofthe exciting signal. It a relatively low frequency or slowly varying DCpotential is applied between the grids, the velocity of the electronsvaries accordingly.

If desired, the velocity accelerating potential may be applied betweenthe grid 16 and the screen 15 of the tubes, or between the grid 16 andthe screen 15, if the grid 18 is eliminated, as illustrated in brokenlines. In order to achieve linear velocity modulation over the entirescan region of the deflection system, it is desirable that theaccelerating potential be applied between substantially parallelsurfaces so that the path of the electron beam is substantially normalto the lines of force of the varying field.

In FIGURE 2, the invention is illustrated as embodied in a colortelevision display system. The television signal is received by anantenna and coupled through radio frequency and intermediate frequencyamplifier 26. The picture information is derived from the receivedsignal and amplified at 27, and split into two portions, the luminanceor brightness information which passes through channel 28 and the colorinformation in channel 29. The synchronizing signals are derived fromthe received signal and sweep circuits 30 generate the deflectionpotentials which are applied to deflection coils 31 around the neck ofcolor display tube 32. A high voltage rectifier 33 derives, from thesweep circuit, a potential which is applied to the screen 34 of thetube. The sound is amplified at 35 and connected with a speaker 36. Thedisplay screen of the tube is coated with a phosphor which is responsiveto a velocity condition of the electron beam to develop a light outputof differing colors. Mounted within the tube, between the deflectioncoils 31 and screen 34 are a pair of spaced grids and 41, both of whichare generally spherical in configuration and have a center coincidinggenerally with the center of deflection of the tube. The colorinformation from color circuitry 29 is coupled to the grids 40, 41 inthe form of varying voltage which establishes a velocity conditionsuitable to stimulate the phosphor of screen 34 causing it to emit lightof appropriate colors corresponding with the received signals. As thetwo grids 40 and 41 are generally concentric about the center ofdeflection, the beam modulating field established between them issubstantially norml to thedeflected beam and a linear modulationcharacteristic is achieved. Thus, modulation of the beam velocity doesnot affect the size or linearity of the picture. A luminance orbrightness signal is coupled from luminance channel 28 to the cathode ofthe display tube.

As pointed out in connection with FIGURE 1, the color signal may beconnected between one of the grids 40-, 41, and the screen 34 of thetube, if desired. Where the modulating signal is connected between grid40 and the tube screen, the grid 41 is omitted.

Turning now to FIGURES 3 and 4, a specific embodiment of the inventionis illustrated. The tube 45 has a screen which includes a glass plate 46on the inner surface of which are deposited three phosphor coatings 47,48

and 49, each of which, when excited by the electron beam, gives off adifferent color. The phosphor layers 48 and 49 are transparent so thatlight emitted by the layers 47 and 48 is visible. The three phosphorlayers may, for example, represent the colors red, blue and green. Atube utilizing such phosphors is available from Pan Aura Corporation,Arlington, Va.

In accordance with the invention, a wire mesh grid 50 is incorporated inthe tube between the center of deflection 51 and screen 46. A suitablesignal from a color signal source 52 is applied between grid 50 andscreen 46 effecting a velocity modulation of the electron beam inaccordance with the color information. As seen in FIG- URE 4, therelationship of grid 50, the center of deflection 51 and screen 46 withits phosphor coatings is such that equipotential lines 53 and 54 aresubstantially at right angles to the paths 55 of the electron beams. Thesignal applied between grid 50 and screen 46 varies the velocity of theelectron beam and thus the energy of the electrons at the time theystrike the screen. The only effect, however, is on the beam velocity.There is no appreciable interaction of the modulation with beamdeflection. The velocity or energy variations of the beam cause theelectrons to penetrate to varying depths of the multiple phosphorcoating on the inner surface of glass plate 46. The principal portion ofthe beam energy is given up at the depth at which the electrons stop.Accordingly, the color of the light output varies with the color signal.

A modified form of the invention is illustrated in FIG- URE 5. Here, thetube 60 has a screen 61 with a single phosphor layer 62 on the insidethereof. The phosphor 62 includes a mixture of different materials whichemit different colored light when excited at different frequencies. Theamount of light given off depends on the average beam velocity at thefrequency of excitation. In this embodiment of the invention anauxiliary grid 63 is pro vided which, again, is generally spherical inconfiguration about the center of deflection 64. The color signal iscoupled to an oscillator 65 which has an output that is variable both infrequency and in amplitude, the frequency representing the hue of thecolor information and the amplitude representing the degree ofsaturation of the color. The output of oscillator 65 is connectedbetween auxiliary grid 63 and screen 62 and causes a velocity modulationof the electrons at a high frequency, resulting in bunching of theelectrons at the oscillator frequency. Again, the modulation is effectedlinearly so that the beam deflection or scanning are not impaired.

FIGURES 6 and 7 illustrate the incorporation of the invention in asingle gun tube utilizing the dot-mask principle. Tube 70 has a singleelectron gun beam source 71. The screen 72 has on its inner surface aphosphor made up of small areas or dots of materials which give offdifferent colors, as red, blue or green, when struck by the electronbeam. Inside the tube and closely adjacent the phosphor coating 73 is ametal plate 74 having therein a series of small holes or apertures 75.Each of the holes is appropriately related to an elemental area of threecolor dots of the phosphor 73 so that the electron beam passing throughthe hole strikes one or a combination of the color dots, determining theresulting color seen by the viewer.

In accordance with the invention, a grid 76, in the tube 70 immediatelyadjacent the deflection zone, has applied thereto from the colorcircuitry 77 a signal which effects a slight diffraction of the electronbeam, resulting in a control of the path of the beam through the maskaperture. This causes the beam to strike an appropriate color dot orcombination of color dots to reproduce the desired hue. In this case,the velocity modulation of the beam is not linear but is intentionallymade slightly nonlinear so that the beam path is altered in accordancewith the color signal. However, the nonlinearity is not great enough toaffect the scan. During the receipt of a white area or of a black andwhite signal, the beam travels through grid 76 without a change indirection and excites each of the color dots.

While I have shown and described certain embodiments of my invention, itis to be understood that it is capable of many modifications. Changes,therefore, in the construction and arrangement may be made withoutdeparting from the spirit and scope of the invention as disclosed in theappended claims.

I claim:

1. In a color display system: a cathode ray tube having a singleelectron emitting and beam forming gun means and having a screen with amulticolor light output de pendent on a condition of the electron beam;means between said gun and said screen to establish a field fordeflecting said beam to scan said screen; means, between said deflectingmeans and said screen, for establishing a beam modifying field with aboundary adjacent the deflecting field which modifying field isgenerally uniform with respect to said deflecting field; and a source ofbeam modifying potential, responsive to the color to be displayed,connected with said field establishing means for imparting to said beama condition modulation to vary the color of light output of said screen,independent of the deflection of the beam.

2. The color display system of claim 1 wherein the color of the screenlight output is a function of a velocity condition of the beam strikingthe screen and in which a grid is located immediately adjacent saiddeflecting means and a velocity modifying potential is applied betweensaid grid and said screen.

3. The display system of claim 2 wherein said deflecting means has anapparent center of deflection and said grid is generally spherical andconcentric with said center.

4. The display system of claim 1 wherein the beam modifying field meanshas a nonlinearity which is less than an elemental area of the display,throughout the entire screen surface.

5. The display system of claim 1 wherein the color of the light outputof said screen is dependent on the energy of the beam striking thescreen and said beam modifying field means responds to the potentialfrom said source to establish an accelerating field which is normal tothe path of the deflected beam throughout the scan thereof.

6. The display system of claim 1 wherein the color of the light outputof said screen is dependent on the frequency of the beam striking thescreen and said beam modifying field means responds to the potentialfrom the source to establish an alternating field normal to the path ofthe deflected beam throughout the scan thereof to frequency modulate thebeam in accordance with said signal.

7. The color display system of claim 1 wherein said screen has aplurality of sets of color dots arranged in a pattern of elemental areaswith an apertured mask immediately adjacent the screen, having aperturestherein related to the dots of each set so that the direction of travelof the beam through each aperture determines the color of excitation ofthe screen and said beam modifying field means responds to the potentialfrom said source to effect diffraction of said beam to vary thedirection of its travel through each hole.

8. The display system of claim 5 wherein the color of the light outputof said screen is dependent on the velocity of the beam striking thescreen and said beam modifying field means responds to the potentialfrom said source to effect a linear variation of the velocity of thebeam throughout the scanning range.

9. The display system of claim 6 wherein the hue of the light output ofsaid screen varies with the frequency of the beam striking the screenand the saturation of the light output varies with the amplitude of thebeam, and in which the source of color signal includes a means f rgenerating a signal having a frequency representing hue and an amplituderepresenting saturation.

10. The display system of claim 9 wherein a grid is interposed betweenthe deflecting means and the screen and the color representative signalis applied between the grid and the screen, to effect bunching of theelectrons of the beam at the frequency of the color representativesignal to excite said screen.

References Cited UNITED STATES PATENTS 2,455,710 12/1948 Szegho 313-9'22,580,073 12/1951 Burton 313-92 2,672,575 3/ 1954 Werenfels 315-212,814,670 11/1957 Templin 313-92 2,928,975 3/ 1960 Williams 313-923,231,775 1/ 1966 Pritchard 313-92 3,265,915 8/1966 Thomas 313-923,290,434 12/1966 Cooper et a1 313-92 3,312,781 4/ 1967 Land 313-92RODNEY D. BENNETT, Primary Examiner.

B. L. RIBANDO, Assistant Examiner.

US. Cl. X.R. 313-92

